as different as chalk and cheese

Translations
совершенно разные
They are as different as chalk and cheese.
Они совершенно разные.
Definitions
A phrase used to describe two things that are very different from each other.
Words
as

adverb
настолько
different

adjective
разные
as

adverb
как
chalk

noun
мел
and

conjunction
и
cheese

noun
сыр